SCIEM E-GOSSIP. 



this line is one i hat is too difficull to del ermine, 

 to be of much practical utility in the field. In the 

 Thames Valley, at any rate, such a difficulty will 

 be found to be purely Lllusionary, for the follow ing 

 reason. The numerous valleys of the side streams 

 which cul transversely through the terraces of the 

 Thames afford magnificent opportunities for the 

 examination of the basal boundaries or levels of 

 i fie various terraces of drift. All I bat is wanted is 

 careful and detailed mapping on either side of the 

 valleystogive us the data required. The information 

 thus obtained may be augmented and made of 

 much greater value to us by the details given by 

 junction sections and borings in the districts 

 between the side valleys. A further objection 

 which may be raised is that on the principle of 

 "whal is sauce for the goose is sauce for the 



gander" -namely, thai the subterranean erosi »f 



percolating water, which, as I have here pointed 

 out, affects the "surface levels," must in doingthat 

 primarily affect the "basal levels." This is true 

 enough, but in being true it opens up an interesting 

 side development. If is clear that such erosion 

 will all'ect calcareous strata to a far greater extent 

 than it will argillaceous rocks. As the greater 

 portion of the drifts of the Thames Valley are 

 situated-upon the London Clay, the effect is but 

 infinitesimal upon the utility of our basal levels 

 as a datum line. Where the chalk crops out and 

 the drifts repose upon it, the effects are far from 

 infinitesimal, for we may find patches of older 

 terraces brought down to approximately the same 

 level as those of newer ones, simply through the 

 lissolution of the calcareous platform, that has 

 gone on since Pleistocene times. If we can deter- 

 mine the amount of lowering that has gone on in 

 ibis manner in the different districts, then perhaps 

 we shall be able to get some idea as to the rapidity 

 of the process. At any rate, many interesting 

 results are likely to accrue from a more general 

 recognition of the importance of the "basal level" 

 of drift, and from a more general employment of 

 it in our classification. Personally I have of late 

 been determining such lines with good results in 

 several districts in the Lower Thames Valley, which 

 results I hope to publish before long. — Martin A. 

 ('. Hinton, c\o J. C. G nihu in. Esq., 2 Garden Court, 

 Temple, E.C., June '2nd, 1900. 



Neolithic Deposit near Brighton. — During 

 a visit to Brighton in the early part of this year I 

 came across a small section to the east of the town 

 showing three feet of chalky rain-wash overlying 

 the Palaeolithic rubble-drift. As the exposure was 

 half-way up the slope, the deposit was probably 

 much thicker lower down. The chief interest 

 connected with this rain-wash lies in the fact 

 that it is full of Neolithic flakes ; while it also 

 yielded a couple of burnt stones. The surface 

 above it is strewn with flint flakes, cores, scrapers, 

 &c, which only differ from the underground speci- 

 mens in being discoloured by oxide of iron and 

 other matter. The occurrence of Neolithic debris 

 in a deposit of this kind is of course no proof that 

 the deposil is of that age ; but in this instance the 

 great abundance of flakes throughout certainly in- 

 dicates that the rain-wash is, in all probability, 

 a Neolithic one. The surface specimens do not 

 supply any e\ idence, as t hey may have been derived 

 from the upper part of the deposit. Near the base 

 I obtained several examples of the following land 

 shells, viz.: — Pupa vi/uscorum Lin., Helix aspersa 

 Mull., //. nemoralis Lin., Helicella itala Lin., 



//. caperata Mont., //. virgata Da Costa, ai i 

 //. earthusiana Mull. These mollusca are all living 

 in the immediate neighbourhood at the present 

 day. Helicella vir gat a is noteworthy, as, although 

 it is known from the Palaeolithic drift of Bam- 

 well and llford. it ha- not hit hi • corded 



Er any later deposil in Britain; that is, on the 



mainland, for it is known from a hill-wash in the 

 [sle of Wight. Helix nenurralis ranges from the 

 forest Bed upward- 1 Helicella '/"/"and H. cape- 

 rata from the Pleistocene; but Helix aspersa is 

 probably a Neolithic introduction into this country, 

 its earliest known appearance as a fossil being in 

 the Neolithic alluvium of the Lea and Kennel 

 valleys. Helicella carl 'In/sin mi al-o seems to be 

 a late arrival in Britain, though it formerly had a 

 much wider distribution than at present. It is now 



limited to the chalk downs of the south-east coast, 

 and does not range north of t he River Stour, though 



it once inhabited East Anglia, as shown by its 

 occurrence in alluvial beds al luitlej and \~ 

 — ,/. P. Johnson, 150 High Street, Sutton. 



A NEW Type OP Rock. — In a paper read 

 the Geological Society on^JfUy 2'.). Messrs. J. B. 

 Hill and H. Kynaston dealt with "a new type of 

 rock from Kentallen and elsewhere." It was 

 originally described by Mr. J. J. H. Teal] under 

 the name of olivine-monzonite, and they regarded 

 it as a type, round which they group a peculiar 

 series of basic rocks discovered in several localities. 

 The rocks consist essentially of olivine and augite, 

 with smaller amounts of orthoclase, plagioclase, 

 and biotite, while apatite and magnetite are ac- 

 cessory. The peculiar feature of the rocks is the 

 association of alkali-felspar with olivine and augite. 

 and the group is related to the shonkinite of 

 Montana and the olivine-monzonite of Scandinavia. 

 The occurrence of the rocks is connected with 

 four neighbouring, but distinct, areas of intrusion. 

 In these areas the new rock is the most basic type, 

 and it occurs in the marginal portions of the areas. 

 Close relationships exist between the different 

 intrusive rocks in each area, so that it may be 

 concluded that these constitute a "rock series" 

 ranging from granite through augite-diorite to- 

 wards the olivine-bearing rocks, in the plutonic 

 phase, and from orthoclase-porphyry and porphyria ■ 

 to augite-lamprophyre, in the dyke and sill phase. 

 The whole assemblage appears to have been 

 derived by a process of differentiation from one 

 parent magma ; and the order of intrusion has 

 been in the main one of increasing acidity. An 

 interesting discussion followed the reading of the 

 paper, but it was felt that the new name of 

 •■ Kentallenite " which had been applied to it was 

 of too local an origin. It was suggested that it 

 should in future be known as "Teallite," after the 

 well-known petrologist, the President of the Geo- 

 logical Society. A series of slides Were exhibited 



upon (he screen, showing well-developed crystals 

 of olivine and augite, with biotite in irregular 

 patches, and orthoclase. &c., fitting in the inter- 

 stices. 



Geology of North Staffordshire.— The 

 Report of the North Staffordshire Field Club for 

 1899-1900 contains several geological notes and 

 articles of more than local interest. In the report 

 of the Chairman of Section E, Geology, Mr. Barke, 

 F.G.S., makes reference to the re-survey of the 

 North Staffordshire Coalfield and surrounding 

 tracts, now drawing to a close. It appears that 

 several results will be of Lrre.it inti rest to geologists. 



